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A285305
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Fixed point of the morphism 0 -> 10, 1 -> 1001.
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4
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1, 0, 0, 1, 1, 0, 1, 0, 1, 0, 0, 1, 1, 0, 0, 1, 1, 0, 1, 0, 0, 1, 1, 0, 1, 0, 0, 1, 1, 0, 1, 0, 1, 0, 0, 1, 1, 0, 0, 1, 1, 0, 1, 0, 1, 0, 0, 1, 1, 0, 0, 1, 1, 0, 1, 0, 0, 1, 1, 0, 1, 0, 1, 0, 0, 1, 1, 0, 0, 1, 1, 0, 1, 0, 0, 1, 1, 0, 1, 0, 1, 0, 0, 1, 1, 0
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OFFSET
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1
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COMMENTS
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This is a 3-automatic sequence. See Allouche et al. link. - Michel Dekking, Oct 05 2020
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LINKS
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FORMULA
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Proof of this conjecture. Let mu: 0 -> 10, 1 -> 1001 be the defining morphism of (a(n)), and let tau: 0 -> 01, 1 -> 0011 be the defining morphism of A284775.
Since mu^n(0) starts with 1 for n>1, mu^n(0) tends to (a(n)) as n tends to infinity. So the conjecture will follow directly from the following claim.
CLAIM: 0 mu^n(0) = tau^n(0) 0 for n>0.
Proof: By induction over two levels, exploiting the obvious equality tau(1) = 0 tau(0) 1 to go from the third to the fourth line below.
For n=1: 0 mu(0)= 010 = tau(0) 0.
For n=2: 0 mu^2(0)= 0100110 = tau^2(0) 0.
Suppose true for n-1 and n. Then
tau^{n+1}(0) =
tau^n(tau(0)) =
tau^n(0) tau^n(1) =
tau^n(0) tau^{n-1)(0) tau^n(0) tau^{n-1}(1) =
0 mu^n(0)0^{-1} 0 mu^{n-1}(0)0^{-1}0mu^n(0)0^{-1}tau^{n-1)(1)=
0 mu^{n-1}(mu(0))mu^{n-1}(0)mu^{n-1}(mu(0))0^{-1}0tau^{n-)(1)=
0 mu^{n-1}(10) mu^{n-1}(0) mu^{n-1}(10) 0^{-1} tau^{n-1)(1) =
0 mu^{n-1}(1001) mu^{n-1}(0) 0^{-1} tau^{n-1)(1) =
0 mu^n(1) 0^{-1} tau^{n-1)(0) 0 0^{-1} tau^{n-1)(1) =
0 mu^n(1) 0^{-1} tau^{n-1}(01) =
0 mu^n(1) 0^{-1} tau^n(0) =
0 mu^n(1) mu^n(0) 0^{-1} =
0 mu^n(mu(0)) 0^{-1} =
0 mu^{n+1}(0) 0^{-1}.
So we proved 0 mu^{n+1}(0) = tau^{n+1}(0) 0.
(End)
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EXAMPLE
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0 -> 10-> 1001 -> 100110101001 ->
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MATHEMATICA
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s = Nest[Flatten[# /. {0 -> {1, 0}, 1 -> {1, 0, 0, 1}}] &, {0}, 10]; (* A285305 *)
u = Flatten[Position[s, 0]]; (* A285306 *)
v = Flatten[Position[s, 1]]; (* A285307 *)
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CROSSREFS
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KEYWORD
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nonn,easy
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AUTHOR
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STATUS
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approved
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